diff --git a/nse_main.lua b/nse_main.lua
index e534c4d5a..d04c19d8c 100644
--- a/nse_main.lua
+++ b/nse_main.lua
@@ -88,6 +88,8 @@ do -- Append the nselib directory to the Lua search path
   package.path = package.path..";"..path.."?.lua";
 end
 
+(require "strict")() -- strict global checking
+
 -- NSE_YIELD_VALUE
 -- This is the table C uses to yield a thread with a unique value to
 -- differentiate between yields initiated by NSE or regular coroutine yields.
diff --git a/nselib/strict.lua b/nselib/strict.lua
new file mode 100644
index 000000000..87b22ba59
--- /dev/null
+++ b/nselib/strict.lua
@@ -0,0 +1,83 @@
+--- Strict Declared Global library.
+--
+-- Checks for undeclared global variables during runtime execution. This module
+-- places the 'strict' function in the global environment. The strict function
+-- allows a script to add runtime checking so that undeclared globals cause
+-- an error to be raised. This is useful for finding accidental use of globals
+-- when local was intended.
+-- A global variable is considered 'declared' if the script makes an assignment
+-- to the global name (even nil).
+--
+-- @class module
+-- @name strict
+-- @copyright Copyright© Same as Nmap--See http://nmap.org/book/man-legal.html
+
+local error = error;
+local getfenv = getfenv;
+local lmodule = module;
+local rawset = rawset;
+local rawget = rawget;
+local setfenv = setfenv;
+local type = type;
+
+local getinfo = debug.getinfo;
+
+local function what ()
+  local d = getinfo(3, "S");
+  return d and d.what or "C";
+end
+
+--- The strict function.
+--
+-- This function adds runtime checking to the global environment for use of
+-- undeclared globals. A global is 'undeclared' if not assigned in the file
+-- (script) scope previously. An error will be raised on use of an undeclared
+-- global.
+function strict ()
+  local _G = getfenv(2);
+
+  local mt = getmetatable(_G) or setmetatable(_G, {}) and getmetatable(_G);
+  local _newindex, _index = mt.__newindex, mt.__index;
+  
+  mt.__declared = {};
+  
+  function mt.__newindex (t, n, v)
+    if type(_newindex) == "function" then
+      _newindex(t, n, v); -- hook it
+    end
+    if not mt.__declared[n] then
+      local w = what();
+      if w ~= "main" and w ~= "C" then
+        error("assign to undeclared variable '"..n.."'", 2);
+      end
+      mt.__declared[n] = true;
+    end
+    rawset(t, n, v);
+  end
+  
+  function mt.__index (t, n)
+    if type(_index) == "function" then
+      local v = _index(t, n); -- hook it
+      if v ~= nil then return v end
+    else
+      local v = _index[n];
+      if v ~= nil then return v end
+    end
+    if not mt.__declared[n] and what() ~= "C" then
+      error("variable '"..n.."' is not declared", 2);
+    end
+    return rawget(t, n);
+  end
+end
+
+local strict = strict;
+
+function module (...)
+  local myenv = getfenv(1);
+  lmodule(...);
+  strict();
+  setfenv(2, getfenv(1));
+  setfenv(1, myenv);
+end
+
+return strict;